Methods and Devices for Color Detection to Localize the Blood Mass of an Intracerebral Hematoma

ABSTRACT

Devices for localizing an intracerebral hematoma or blood mass in brain tissue. The devices include an elongate probe a color sensors and a light emitter on the distal end of the probe. The color sensors produce a signal corresponding to the color of light reflected into the color sensors. A display is provided to indicate the color detected.

This application claims priority to U.S. Provisional Application62/337,498 filed May 17, 2016,

FIELD OF THE INVENTIONS

The inventions described below relate to the field of minimally invasivebrain surgery.

BACKGROUND OF THE INVENTIONS

Stroke is a common cause of death and disabling neurologic disorder.Approximately 700,000 patients suffer from stroke in the United Statesevery year. Hemorrhagic stroke accounts for 20% of the annual strokepopulation. Hemorrhagic stroke is due to a rupture of a blood vessel inthe brain, causing bleeding into the brain tissue and resulting in ahematoma (a blood mass) in the brain. Prompt removal of the blood massis necessary to limit or prevent long-term brain injury. Clearvisualization and imaging of the blood mass and any surrounding surgicalfield facilitates removal of the blood mass. Removal and visualizationcan often be accomplished through a cannula and obturator assembly,placed through a hole drilled in the skull near the site of thehematoma. The site of the hematoma can be accurately identified using aCT scan. To aid in placement of the cannula and obturator assemblyprecisely at the hematoma, and also to aid in inserting the cannulathrough a route least likely to damage healthy brain tissue,neurosurgeons use sophisticated and costly stereotactic surgery systemsor neuro-navigation systems. These systems depend on previously obtainedMRI or CT scans, which may be several hours old, and thus not perfectlyreflective of the shape and location of the blood mass at the time ofsurgery. In these systems, visual confirmation that the cannula distalend is properly positioned can be accomplished only after the obturatorhas been removed from the cannula. If the distal end has not beenaccurately placed, the obturator must be re-inserted, and the cannulaand obturator assembly must be manipulated, perhaps repeatedly, until,after removal of the obturator, the blood mass is visible. A lesssophisticated method, used before these expensive neuro-navigationsystems and stereotactic systems became standard and still used wherethese systems are not available, involves large craniotomies,exploration and direct visual search for a blood mass, extensive tissuedissection, and invasive instrumentation, all associated with highmortality and morbidity.

SUMMARY

The devices and methods described below provide for a probe forlocalizing a blood mass in a patient's brain. The probe has one or morecolor sensors and a light emitter on the distal end and a display on theproximal end. The color sensors produce a signal corresponding to thecharacteristics of light reflected into the color sensors. A controlleris operatively connected to the color sensors to convert the signal todata suitable for display to a user through the display, and the displayis operatively connected to the controller for visualizing a color,data, one or more graphs and/or an audible signal corresponding to thetissue reflecting light to the color sensors. The display may be asimple light, operable to display color corresponding to the colorsensed by the color sensors. This visual feedback is provided to theuser of the probe during use, while the user is pushing the probethrough the brain to reach and find a blood mass. The probe may be usedalone, to locate a blood mass, or in combination with an aspirator tolocate and then aspirate the blood mass, or in combination with acannula or sheath (with the probe serving as an obturator), or as aguide wire or stylet for an aspiration catheter to be navigated into thebrain, over the stylet, or in combination with a neuro-navigation systemto confirm proper location after insertion of a probe or sheath understereotactic or neuro-navigation guidance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a patient with an intracerebral hematoma.

FIGS. 2 and 3 illustrate a blood mass localizer which includes a colorsensor assembly.

FIGS. 4 and 5 illustrate a blood mass localizer with a discrete display.

FIGS. 6 through 10 illustrate steps for localizing and removing theintracerebral blood mass from the patient of FIG. 6.

FIGS. 11, 12 and 13 illustrate different embodiments of the probe whichcan be used in different methods of accessing a blood mass.

DETAILED DESCRIPTION OF THE INVENTIONS

FIG. 1 illustrates a patient 1 with an intracerebral hematoma or bloodmass 2 in brain tissue 3. Blood and blood clots such as blood mass 2 arered to red/black, and the surrounding brain tissue 3 is white oroff-white. The ventricles 4 contain cerebrospinal fluid, which iscolorless. As described below, a probe fitted with a color sensorassembly can be used to navigate through the brain and detect when theprobe tip enters the blood mass or the ventricles.

FIG. 2 illustrates a blood mass localizer 9 which includes a probecomprising a slender rod 10 which has a proximal end 10 p and a distalend 10 d. The distal end is adapted for transcranial insertion into thebrain of a patient. The proximal end resides outside the skull duringuse. The probe can comprise a cannula or trocar, an obturator or asheath, a guide catheter, a stiff wire or probe, a needle, or anaspiration tube. The device illustrated in FIG. 2 is a simple probe,with a small diameter for the entire length of the device. The distalend 10 d of the probe includes color sensor assembly 11 and one or morelight sources such as light source 12 which produces white light and/orinfrared light, or, at least, light of several wavelengths, or, insingle color embodiments, a single-color light such as red. As shown inthe detail view of FIG. 3, the color sensor assembly and the lightsource may be embedded in a clear lens or boss 13 of clear epoxy orplastic. Preferably, the light source is disposed proximal to the colorsensor, as shown in FIG. 3. The color sensor assembly 11 includes one ormore light sensors such as sensor 14R, 14G, 14B and 14W (shown in FIGS.3 and 4), which sense light of different colors, which preferablyinclude one or more of red, green, blue, and white (an infrared lightsensor can also be included, for use as described below). Thus, thecolor sensor may be multi-color sensor or a single-color sensor. Theproximal end 10 p of the localizer includes a display 15, such as amulti-color LED, OLED or PLED array, which is operably connected to thesensor assembly 11 through a suitable controller 16. The controller isoperable to receive signals from the color sensor assembly 11(corresponding to intensity of light detected by each color sensor) andproduce an output signal (or signals) corresponding to the color(s)detected by the color sensor assembly. The controller operates thedisplay 15, such that the display displays a color that mimics the colorof any light detected by the color sensor assembly 11. A battery orpower source and circuitry needed to operate and power the color sensor,controller and display may be disposed anywhere in the device. The lenscan be configured with additional optical elements, or augmented withprisms to direct light reflected from tissue off-axis from thelongitudinal axis of probe and rod.

For “over-the-wire” use, the probe may consist of the rod, the colorsensor assembly, the light source, which may be encapsulated in thelens, and the display and the controller, all disposed on or within aprobe of small diameter suitable for insertion through brain tissue andsubsequent insertion of a sheath, cannula or shunt over the probe (whilethe probe remains in the brain).

The color sensor assembly 11 is preferably an RGBW color sensor assemblywith light sensor(s) 14R, 14G, 14B and 14W to detect light of variouscolors and produce signals corresponding to the detected colors (one ormore frequencies or wavelengths and the intensity or power of light atthe one or more frequencies or wavelengths incident on the sensors suchas red, green, blue or white light, in the case of an RGBW sensorassembly). The color sensor assembly is preferably an RGBW(red-green-blue-white) color sensor assembly, but the system can beimplemented with alternate color sensors such as RGB color sensors,cyan-magenta-yellow (CMY); cyan-magenta-yellow-black (CMYK);hue-saturation-value (HSV) or hue-saturation-lightness (HSL). The colorsensor assembly produces signals corresponding to the frequency andintensity of the light incident on the sensors. For example, an RGBWcolor sensor provides signals corresponding to the intensity of red,green, blue and white light incidents upon the sensors. Moresophisticated imaging devices, distinct from color sensors, such asCCD's, CIS or CMOS image sensors may be used, though full image data isnot necessary. The controller 16 is operably connected to color sensorassembly 14 and optionally to light source 12, to operate the lightsource to emit light into surrounding body tissue (to illuminate thebody tissue and cause reflected light to reach the sensors) and receivesensor data from each sensor (corresponding to the reflected lightdetected by each sensor) and convert it to a useful format (signaluseful to operate the display) and forwards output signals to thedisplay to cause the display to present information to a usercorresponding to the color of tissue proximate the color sensor.

FIG. 4 illustrates a blood mass localizer 9 configured as an elongateprobe which includes the color sensor assembly 11 and light source 12and a textual display. As with the device of FIG. 2, the sensor assemblyproduces signals that the controller uses to produces output signals tothe display to cause the display to present information to a user. Inthis system, the display 15 may be remote from the localizer, and maytake the form of a computer display (such as a CRT, LED display, or thelike) or a small LCD display. The controller may be located anywhere inthe system. The color data provided to a user may be displayed as textdescribing body tissue matching the color detected by the color sensors,such as “BLOOD” or “BRAIN”, or, as shown in FIG. 5, as one or morenumbers corresponding to intensity of light received by each sensor, oras a color patch on the display, a series of color patches (one for eachsensor) a bar graph, or any other useful indicia or image useful tocommunicate to a use the color of tissue proximate the color sensingassembly. The system may also include a speaker, operable by thecontroller, to provide audible prompts to the user corresponding to thecolor detected by the color sensing assembly. Additional color sensorsmay be positioned along the length of the probe, and around thecircumference of the probe, to provide color feedback for tissue aboutthe probe proximal to the distal tip of the probe.

FIGS. 6 through 10 illustrate the use of the blood mass localizer 9 tolocate and map an intracerebral blood mass such as blood mass 2. This isillustrated with the localizer 6 in the configuration shown in FIG. 2.

As shown in FIG. 6, a surgeon inserts distal end 10D of probe 10 withsensor assembly 11 on the distal end of the probe, to find and localizeblood mass 2. The surgeon advances the probe through brain tissue 3until reaching the blood mass 2, while operating the localizer,including operating the LED light source 12 to emit light intosurrounding tissue and operating the color sensor assembly to detect anylight reflected, and operating the display 15 to indicate thepredominant color of reflected light incident on sensor assembly 11.When the color sensor assembly is disposed within brain tissue, which iswhite or off-white, the color sensor assembly detects this color, andthe controller causes the display to illuminate the display, to emitcorresponding white or off-white color. As the color sensor approachesthe blood mass, as shown in FIG. 7, the color sensor will, detectincreasing intensity of red light reflected from the blood masstransmitted back to the color sensor through the surrounding braintissue. In this instance, the controller causes the display toilluminate the display, to emit corresponding pale red. Upon furtheradvancement of the color sensor assembly, such that the color sensorassembly enters the blood mass as shown in FIG. 8, and the color sensorassembly detects the red color corresponding to blood mass, thecontroller causes the display to illuminate the display, to emitcorresponding red. This indicates that color sensor assembly 11 is inthe blood mass 2 as illustrated in FIG. 8. As illustrated in FIG. 8, thedisplay 15 indicates a predominantly red color as long as sensorassembly 11 is within the blood mass 2. As the probe 10 is advancedthrough the brain and blood mass, the color sensor assembly 11 willeventually approach the distal margin of the blood mass and exit theblood mass as illustrated in FIG. 9. As the color sensor assembly 11nears the margins of the blood mass, light reflected to color sensorassembly 11 begins losing the predominant red color, and the coloremitted by display 15 (as controlled by the controller) changes to apink color to suggest the nearing brain tissue 3. If advanced past theblood mass, such that the color sensor assembly re-enters brain tissue,the controller will cause the display to emit, again, a white oroff-white color corresponding to the color of the brain tissue.

The controller may be configured or programmed to provide a displaycorresponding to detected color that, rather than closely mimic thedetected color, indicates the detected color in a step-wise fashion. Forexample, the controller may be configured or programmed to emit redlight indicative of a blood clot when the detected color ispredominantly red (a combination of relative intensities and ratios ofdetected color, such as a ration of red to green greater than 1.5 andrelative output count for red greater than 5000 (on a scale of 0 to65000 as provided by a Vishay VEML6040 sensor). With the controllerconfigured or programmed and operated in this fashion, the display willnot transition gradually from white to red when approaching the bloodmass, but will shift to red quickly when the probe tip encounters blood(as indicated by reaching the threshold intensity of the detected redlight).

With the location of the blood mass confirmed, the surgeon can removethe blood mass. The surgeon may do this by aspiration, with suctionapplied through an aspiration catheter delivered to the blood mass.(This can be accomplished, depending on the configuration of thelocalization device, by delivering a suction catheter to the blood massover the localizer (where the localizer comprises a wire), applyingsuction through the localizer (where the localizer also comprises anaspiration tube), swabbing the blood mass with swabs delivered throughthe localizer, or aspirating the blood mass with an aspiration tubedeliver through the localizer (where the localizer comprises a cannula),etc.) Once a device for evacuating the blood mass is located withinblood mass 2 the blood mass may be evacuated. The blood mass localizermay remain in place to monitor the progress of the blood massevacuation. As a result of the removal of the blood mass, thesurrounding brain tissue will collapse about the distal tip of theaspiration catheter and/or distal tip of the localizer, as illustratedin FIG. 10. As the blood mass is removed and the brain tissue collapses,the blood/brain margin will approach the color sensor assembly (that is,the amount of blood between the color sensor and the brain tissue willdecrease) and the color sensor assembly will begin to detect increasingamount of white light. Consequently, the controller will operate thedisplay to emit an increasing amount of white light, and a relativelydecreasing amount of red light.

Although described above primarily in terms of an RGBW color sensor, thesystem can be implemented with a single-color sensor and/or asingle-color LED, OLED or PLED (a single emitter or an array). Forexample, a red color sensor may be used alone, without the coincidentuse of green, blue and white sensors, to detect a red blood mass insurrounding white brain tissue. In this instance, the controller ispreferably operable to operate the display to indicate that the probetip is in brain tissue when the detected intensity of red light is low,below a predetermined threshold, and indicate that the probe tip is inblood when the detected intensity of red light is high, above apredetermined threshold, without also operating additional color sensorsto positively detect brain tissue by detecting white light or otherlight.

The localizing device can be used to detect CSF at the probe tip, forlocating the ventricles or cysts in the brain (or even the CSF betweenthe dura and the brain. CSF is a clear, colorless fluid, such that withthe color sensor assembly disposed within CSF, very little light emittedfrom the light source will be reflected by the CSF (compared to thelight levels reflected by brain tissue). Thus, a low level of detectedlight, compared to the level detected in brain tissue, will provide anindication that the probe tip has entered a reservoir of CSF. That is,if all colors detectable by the color sensor assembly are detected atlow intensity relative to brain tissue, this is indicative that theprobe tip is in CSF. Thus, to detect colorless CSF, the controller isoperable to receive color sensor data from the color sensor assembly,compare corresponding to the color of tissue surrounding the colorsensor assembly, and operate the display to provide an indication to theuser that the probe tip is disposed within CSF. Infrared light can alsobe used to determine that the distal end of the probe has enteredcerebrospinal fluid, by providing an infrared light source and infraredcolor sensor. CSF is more transmissive to infrared light, compared tobrain tissue, so that a lower level of infrared light detected by theinfrared sensor during use indicates that the probe distal end hasencountered CSF (normally this indicates that the probe tip has enteredthe sinus). Thus, when the information corresponding to the intensity ofinfrared detected by the infrared sensor assembly changes frominformation corresponding to the infrared reflectance/transmissivity ofblood or brain tissue to information corresponding to the infraredreflectance/transmissivity of CSF, the controller operates the displayto display a corresponding color (a false color, such as yellow ororange).

Instead of using light, the probe may be configured to use conductivityand conductivity sensors (or, conversely, the resistivity or impedance)to detect and differentiate tissues such as CSF, blood, and tumor frombrain tissue. For example, CSF is significantly more conductive thanbrain tissue, so that the location of the probe tip within CSF can bedetermined on the basis of measured conductivity of tissue surroundingthe probe tip. Brain tissue typically has conductivity of 0.25 S/m to0.28 S/m (a resistivity of about 3.5 to 4 ohms/m). CSF has aconductivity of about 1.5 to 2 S/m (both at standard conditions of bodytemperature, tested at 40-70 Hz). To use a probe to localize a volume ofCSF within the brain, an elongate probe, similar to that describe inFIG. 2, may be fitted with a pair of electrodes at the distal tip, andwith the controller being operable to operate the electrodes receiveelectrical signals from the electrodes corresponding to the resistivityof the tissue surrounding the probe tip and the operate the display toprovide output to the user to indicate whether the probe tip is disposedin brain tissue or CSF. The probe may also include a pressure sensor,operable to detect pressure exerted by body tissue on the sensor. Thepressure sensor can be used to detect, or confirm, passage of thesensor, and probe tip, from the brain tissue into the sinus (thepressure of CSF in the cerebral sinus is typical lower than tissuepressure in the brain tissue).

The display described above is a convenient means for providinginformation to a user. It may be augmented with audible prompts orhaptic feedback. For example, the system can include a speaker orannunciator (bell, buzzer, beeper or speaker), operable through thecontroller, to provide audible signals corresponding to the colordetected by the color sensor. The annunciator can also function as aproximity warning, by providing a distinct audible signal (for example,beeping with increasing frequency) when the color sensor detects colorindicative of an approaching margin during aspiration. (The controllercan also be operable to operate the visual display to indicate theapproaching margin, by flashing the display or providing other graphicaloutput.)

The controller may comprise a digital or analog image signal processor(depending on the color sensor or image sensor) operable to convert thesensor data to input to the light or display, or it may comprise amicrocontroller, a general-purpose computer, or the controller maycomprise a special purpose computer, or similar device which comprises aprocessor and memory including program code with the memory, where thecomputer program code is configured with the processor to cause thesystem to perform the functions described throughout this specification.The controller may be disposed within the rod itself (as in FIGS. 2 and11), in a handle at the proximal end of the probe (as in FIG. 12), or inan associated computer operably connected to the probe.

The probes can be provided with steering mechanism, operable to bend orsteer the distal end of the probe, deflecting it from the longitudinalaxis of the proximal portions of the probe. The steering mechanism cancomprise a two-wire pullwire system with an appropriate actuatingmechanism on the proximal end of the probe.

FIGS. 11, 12 and 13 illustrate different embodiments of the probe whichcan be used in different methods of accessing a blood mass. FIG. 11illustrates the probe in a form that can be used in conjunction with acatheter or sheath, in an over-the-wire method, to access a blood massin the brain. This probe may be a complete probe, though consisting ofthe rod, the color sensor assembly, the light source, which may beencapsulated in the lens 13, the display 15 disposed on the proximal endof the rod (on the proximal facing surface of the proximal end of therod, with the display transverse dimension being smaller than thediameter of the rod, such that the display does not extend beyond thediameter of the rod) and the controller, all disposed on or within aprobe of small diameter suitable for insertion through brain tissue andsubsequent insertion of a sheath or cannula over the probe (while theprobe remains in the brain). A surgeon may insert this probe into thebrain, and, afterward, the surgeon may slip a short catheter 20 over theproximal end 10 p of the rod, and push it distally over the entire probeuntil the catheter distal end is positioned in the brain proximate theblood mass. After the catheter distal end is placed proximate the bloodmass, the surgeon removes the probe and may use any appropriate surgicaltool (an aspirator, macerator, grasper, ablation probe) inserted throughthe catheter to remove the blood mass or otherwise treat the brain, ormay apply suction to the catheter itself to aspirate the blood mass andremove it from the brain, inject medication or medically manage thesource of bleeding and leave an indwelling drainage catheter andpressure monitor.

FIG. 12 illustrates a probe that can be used as an obturator incombination with a cannula or sheath. The probe is configured to fitinto the lumen of a cannula or sheath 21 suitable for insertion into thebrain while disposed over the probe. The distal end of the probe issized to function as an obturator for use with the sheath. The lens 13may serve as the atraumatic tip of the obturator. The probe comprisesthe rod 10, the color sensor assembly, and a proximal housing 22 whichhouses the control system, power source and the display 15 (which, inthis embodiment may be a simple LED or equivalent lamp operable todisplay colors corresponding to the sensed color). The housing and itscomponents may be permanently fixed to the rod, through any appropriateconnector 23. This configuration may be assembled as an obturator/sheathcombination, and a surgeon may insert the assembled system, with the tipof the probe extending slightly from the distal end of the sheath, untilthe distal end of the assembly is positioned as desired, based on thecolor sensed and the color displayed on the display indicates that thedevice is positioned as desired. The surgeon will then remove the probefrom the sheath, and may use any appropriate surgical tool (anaspirator, macerator, grasper, ablation probe) inserted through thecatheter to remove the blood mass or otherwise treat the brain, or mayapply suction to the catheter itself to aspirate the blood mass andremove it from the brain, inject medication or medically manage thesource of bleeding and leave an indwelling drainage catheter andpressure monitor.

FIG. 13 illustrates the probe in a form that can be used over-the-wireor as an obturator or as a stand-alone device. In the device of FIG. 13,the housing 22 and its components are releasably attached to rod 10through a releasable electrical connector 24 which allows easyseparation and reattachment of the components, intra-operatively,without the use of tools. The releasable electrical connector may, asshown in FIG. 13, be configured to allow detachment of the rod proximaland 10 p from the connector, so that the rod may be used in the over thewire method described above, or may be configured to allow detachment ofthe rod and connector from the housing. The probe may also be configuredwith the rod permanently fixed to the housing, such that the componentscannot be readily separated.

A neuro-navigation marker 25, shown in FIG. 12, may be incorporated intoeach embodiment illustrated.

The devices and methods described below provide for a method forlocalizing a blood mass in a patient's brain by providing an elongateprobe having a distal end and a proximal end, with a color sensorassembly operable to detect a plurality of colors in tissue proximatethe distal end of the probe and generate a signal corresponding each ofthe plurality of colors detected by the color sensor assembly and thenproviding a display operable to display information corresponding to thecolor detected by the color sensor assembly, and then inserting thedistal end of the probe into the patient's brain, and then advancing thedistal end of the probe through the patient's brain, while operating thedisplay to display information corresponding to the intensity of eachcolor detected by the color sensor assembly observing the display, andthen determining that the distal end of the probe is disposed withinbrain tissue or a blood mass, based on the displayed informationcorresponding to the intensity of each color detected by the colorsensor assembly.

The devices and methods described below provide for a device forlocalizing a blood mass in a patient's brain. The localizing deviceincludes an elongate probe having a distal end and a proximal end andone or more color sensors and a light emitter on the distal end of theprobe. The color sensors produce a signal corresponding to thecharacteristics of light reflected into the color sensors. A controlleris operatively connected to the color sensors to convert the signal todata suitable for display to a user, and a display is operativelyconnected to the controller for visualizing data corresponding to thetissue reflecting light to the color sensors.

In the context of this application, localize or localization means tofind or identify the location and extent of a mass such as anintracerebral blood mass in brain tissue, and the term localizer refersto a device operable to be inserted into the body to determine thelocation of a type of tissue within a mass of other tissue.

While the preferred embodiments of the devices and methods have beendescribed in reference to the environment in which they were developed,they are merely illustrative of the principles of the inventions. Theelements of the various embodiments may be incorporated into each of theother species to obtain the benefits of those elements in combinationwith such other species, and the various beneficial features may beemployed in embodiments alone or in combination with each other. Otherembodiments and configurations may be devised without departing from thespirit of the inventions and the scope of the appended claims.

1. (canceled)
 2. A device for localizing a structure in a patient'sbrain, said device comprising; a rod having a distal end and a proximalend, said distal end adapted for transcranial insertion into the brainof a patient, said rod having a substantially constant diameter alongits length; a color sensor assembly disposed on the distal end of rod; alight, operable to display color corresponding to the color sensed bythe color sensors, disposed on the proximal end of the rod; a lightemitter in the distal end of the probe; a controller operable to receivesignals from the color sensor assembly and operate the light, such thatthe display displays a color that mimics the color of any light detectedby the color sensor assembly.
 3. The device of claim 2, wherein thelight has a transverse dimension smaller than the diameter of the rod,such that the display does not extend beyond the diameter of the rod,and the light is disposed on a proximal facing surface of the proximalend of the rod.
 4. The device of claim 2, further comprising a proximalhousing secured to the proximal end of the rod, wherein the light isdisposed on the housing.
 5. The device of claim 4, wherein the housingis releasably attached to the proximal end of the rod.
 6. The device ofclaim 2 wherein the light comprises a multi-color LED, OLED or PLEDarray.
 7. The device of claim 2 wherein the light comprises asingle-color LED, OLED or PLED.
 8. The device of claim 2 wherein thedistal end of the rod is configured as an obturator, and is sized tomatch a lumen of a sheath.
 9. The device of claim 2 wherein the colorsensor assembly comprises a multi-color sensor operable to detect lightof different colors.
 10. The device of claim 2 wherein the color sensorassembly comprises a single-color sensor operable to detect light of asingle color. 11-19. (canceled)
 20. The device of claim 2 wherein thelight emitter comprises an infrared light source.
 21. A method forlocalizing a blood mass in a patient's brain comprising the steps:providing an elongate probe having a distal end and a proximal end, witha color sensor assembly operable to detect color in tissue proximate thedistal end of the probe; providing a display operable to displayinformation corresponding to color detected by the color sensorassembly; inserting the distal end of the probe into the patient'sbrain; advancing the distal end of the probe through the patient'sbrain, while operating the display to display information correspondingto color detected by the color sensor assembly while observing thedisplay; and determining that the distal end of the probe is disposedwithin brain tissue or a blood mass, based on the displayed informationcorresponding to the intensity of color detected by the color sensorassembly.
 22. The method of claim 21, further comprising the step of:determining that the distal end of the probe has entered the blood masswhen the information corresponding to color detected by the color sensorassembly changes from information corresponding to the color of braintissue to information corresponding to the color of a blood mass. 23.The method of claim 22, further comprising the step of: continuing toadvance the distal end of the probe, and determining that the distal endof the probe has exited the blood mass and entered brain tissue when theinformation corresponding to color detected by the color sensor assemblychanges from information corresponding to the color of the blood mass toinformation corresponding to the color of brain tissue.
 24. The methodof claim 23, further comprising the step of: determining a dimension ofthe blood mass based on the depth of the probe upon entry into the bloodmass and the depth of the probe upon exit from the blood mass.
 25. Themethod of claim 21 wherein the probe is provided in the form of acannula.
 26. The method of claim 21 wherein the probe is provided in theform of a stiff wire.
 27. The method of claim 21 wherein the probe isprovided in the form of an obturator.
 28. The method of claim 21 whereinthe probe is provided in the form of a trocar.
 29. The method of claim21 wherein the probe is provided in the form of a catheter.
 30. Themethod of claim 21, wherein the step of displaying informationcorresponding to color detected by the color sensor assembly isaccomplished by operating an LED, OLED or PLED array to display a colorcorresponding to the color detected by the color sensor.
 31. The methodof claim 21, wherein the step of displaying information corresponding tocolor detected by the color sensor assembly is accomplished bydisplaying color patches on a display screen.
 32. The method of claim21, wherein the step of displaying information corresponding to colordetected by the color sensor assembly is accomplished by displaying agraph of intensity of each color detected by the color sensor assembly.33. The method of claim 21, wherein the step of displaying informationcorresponding to color detected by the color sensor assembly isaccomplished by displaying alphanumeric indicia corresponding to theintensity of each color detected by the color sensor assembly.
 34. Themethod of claim 21, wherein the provided color sensor includes aninfrared sensor.
 35. The method of claim 34, further comprising the stepof: determining that the distal end of the probe has enteredcerebrospinal fluid when the intensity of infrared detected by theinfrared sensor assembly changes from an intensity corresponding toblood or brain tissue to an intensity corresponding to cerebrospinalfluid.